According to the prior art there are three basic methods for the desalination of sea water:
1. obtaining water by changing its state, i.e. by evaporation or crystallisation;
2. desalination by electrolytic processes; and
3. reverse osmosis.
The evaporation and distillation of water, for example, requires an energy input of approximately 25 to 30 kWh/m.sup.3 water and hence involves a high energy input, with the heat supplied being at least largely lost in the process. Distillation plants also have the disadvantage that they are exposed to a high risk of corrosion, making it necessary to replace the surfaces coming into contact with the sea water after 11/2 to 2 years. The productivity of these distillaiton plants is restricted to a maximum of 1000 m.sup.3 per day.
The freezing process is based on the formation and growth of individual crystals on which only chemically homogeneous substances agglomerate, whereas foreign particles find no place in the lattice. The formation of inter-crystalline zones in which foreign particles can settle takes place in aqueous solutions when approximately 50% of the salt solution has changed into the solid state. The refrigeration units required for freezing in this way also operate at a low efficiency, and yet are very complex in terms of process technology. In any event, in practice the options described are relatively costly.
In the case of electrodialysis the ions are extracted directly from the salt solution; the ions give up their charge and the metal atmos formed in this way settle on the cathode. This process is in principle applicable only for weak solutions, but not for the desalination of sea water, since the ion concentration is 10.sup.5 per liter of solution. Attempts to reduce the ion concentration by using ion filters are unsuitable since these filters become unusable after a short time because of the ions deposited there. The problem of corrosion is also prominent in the case of electrolytic processes.
Niether has the so-called reverse osmosis process been technically successful, since the water quantities produced in the largest experimental plants barely exceeds 1000 liters per day. In reverse osmosis the salt solution is pressed through cellulose acetate membranes at pressures of 50 bar, or sometimes up to 100 bar. The mechanical stress on the membranes is correspondingly high. A disadvantage of this desalination method is that the membranes become unusable after a long period of use for various reasons, e.g. bacterial attack. Reverse osmosis admittedly has the advantage over the previously described methods that only small quantities of energy are used, by this cannot outweigh the disadvantages of low productivity and the danger of damage to the membranes.
Furthermore, the problems of energy supply in the future can by no means be regarded as solved. The combustion of fossil fuels produces carbon dioxide, of which the increasing proportions in the atmosphere bring the danger of very serious climatic consequences. The obtaining of energy by nuclear fission has created problems concerning the elimination of the radioactive waste. Obtaining energy from solar sources or by wind power devices admittedly has the advantage of producing no waste, but has to be regarded as a failure in economic terms.
Hence there is still an urgent need for the creation of new sources of energy which can be used economically and without pollution of the environment.